Does the dye/soda ash/water mixture stay “active” indefinitely, or is there a fixed working time?

Name: Rose
Country or region: New York, USA
Message: Hi, Does the dye/water mixture and does the dye/soda ash/water
mixture stay “active” indefinitely or is there a fixed working time for
both? Thank you.

I’m assuming you are talking about Procion MX type fiber reactive dyes; answers will be completely different for other classes of dyes. There are three different questions here: soda ash, dye dissolved in water, and dye dissolved in water with soda ash added.

1. Soda ash alone, no dye mixed, in plain water, stays good indefinitely. It never spoils. Dry soda ash may absorb a little water from the air so that a given weight or volume actually contains less than you might expect. Not a big deal since we tend to use more soda ash than we really need to anyway. Cover the bucket, when you put it away for the day, to reduce evaporation and prevent rain from falling in. You can use a soda ash solution for weeks, even months, after preparing it.

2. Fiber reactive dye plus water alone (no soda ash) lasts only until the dye reacts with the water it’s dissolved in. This process is called hydrolysis. You can keep your dye stock solutions for a week or possibly more, and they’ll still be good, if not even a single drop of soda ash has gotten into them; if you refrigerate them, they will last three times as long. This is assuming you have average water, or use distilled water; alkaline or acidic water will badly shorten the lifespan of reactivity of the dye. Note that different dye colors have different hydrolysis rates, so a mixture of different dyes will shift in hue, as the fastest-reacting members of the mixture go bad!

3. The dye/soda ash/water mixture maintains its strength for only a brief
period of time; it may go bad an hour after the soda ash is added to the
dye! Be completely ready with everything else before you add soda ash to the dye. In high-water-ratio immersion dyeing, do not add soda ash until after the dye has had time to penetrate the fabric, and, for smoothest results, then add the soda ash in three or more parts, stirring for a few minutes after each addition, rather than adding all the soda ash at once. You cannot reuse a fiber reactive dye dyebath.

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